This Flightmare was the dragon that attacked Berk every ten years. It paralyzed Astrid's uncle Fearless Finn Hofferson with its mist. This led to the rumor that he froze with fear, thus tarnishing his title and the entire Hofferson House.
Ten years after Fearless Finn Hofferson was killed, Hiccup, Toothless and Astrid went to go after the Hofferson's Bane to observe it and to find out why it was attacking Berk. When they first saw and encountered it, Astrid jumped off Toothless and was ready to fight the dragon. It froze and paralyzed her with its mist, though it was only temporary.
They then followed the Hofferson's Bane until they found the reason why it was attacking Berk. The Hofferson's Bane was following a river of Glowing Algae, its main food source. While Hiccup was inspecting the algae, Toothless drank some of the glowing algae, which caused him to glow. When the Hofferson's Bane found the now glowing Toothless, it became extremely aggressive.
Usually, Toothless' scales would blend perfectly with the night sky, but since he drank from the river, his body started to glow, making him unable to hide from the Flightmare. It chased and attacked the two, but lost them when they hid inside a cave. After some time, the glow wore off.
Later on Fishlegs, Meatlug and Stormfly arrived to help Hiccup and Astrid. After being briefed about what they had learned, Fishlegs made a plan to stop the Flightmare. By cutting a new channel for the river to go out to sea, the Hofferson's Bane would be forced to follow it. They started to do just that until the Hofferson's Bane arrived. Thinking that they were stealing its food, it started to attack them. Hiccup, Astrid, and their dragons kept the Flightmare at bay, while Fishlegs and Meatlug continued to create the new channel.
Once it was done, the algae flowed into the sea, prompting the Flightmare to chase after its food. It hasn't appeared on Berk since then.
The Hofferson's Bane is an aggressive and fast opponent to battle. Its abilities consists of:
Glowing Body: The Flightmare has a spectacular glow, which is the result from eating from the glowing algae. It can control its glow, from being extremely bright to normal. It can turn its glow on bright in order to scare off other dragons who are trying to attack it.
Mist Breath: Instead of breathing fire, the Hofferson's Bane breaths a blue toxic mist that paralyzes its prey. Being continuously breathed with this mist will eventually cause death.
Speed: The Flightmare is able to fly at high speeds, as it managed to keep up with Toothless.
Stamina: It shows no sign of weakness or being exhausted after a long flight.
Banshee-Like Scream: It can scream with a noise so loud that it makes dragons and humans disorientated.
The Hofferson's Bane was the first of its species to ever be seen.
It is possible that this Flightmare is actually Viggo's Flightmare, since it travelled across the sea to an unknown location
Even though this dragon looks like any ordinary Flightmare, which are neon blue, Hofferson's Bane in Rise of Berk is pink in color.
When asked why this is, the developers of Rise of Berk commented that Hofferson's Bane acquired a blue color because of the algae it ate.
However, the change was likely to differentiate it from other Flightmares.
Unlike Viggo's Flightmare, Hofferson's Bane has pupils in his eyes and there is a difference in size, scream, mist, and the shades of blue.